All-wave antenna and coupler system



y 0, 1938. R. B. DOM; 2,117,154

ALL-WAVE ANTENNA AND COUPLER SYSTEM Filed Aug. 27, 1937 Robert B. Dome,

l-hs Attorney.

Patented May 10, 1938 PATENT OFFICE ALL-WAVE ANTENNA AND COUPLER SYSTEM Robert B. Dome, Bridgeport, Conn, assignor to General Electric Company, a corporation of New York Application August 27, 1937, Serial No. 161,247

5 Claims.

My invention relates to radio receiving systems adapted for both long and short Wave reception, and particularly to antenna and coupling arrangements for such systems wherein noise picked 5 up by the transmission line extending between the antenna and the receiver is reduced in both the long wave and the short wave bands. The object of the invention is to provide an improved and simplified antenna and coupler arrangement of this character.

It has been proposed heretofore to provide an antenna and coupler arrangement for all-Wave radio receiving systems comprising a dipole antenna, a transmission line connecting the antenna to the receiver, and a transformer arranged at the antenna in such manner that short wave currents, which cause opposite ends of the antenna to oscillate in opposite phase, produce circulating currents in the transmission line or currents which flow down one conductor of the line and up the other conductor, and that long wave currents, which cause the antenna to oscillate as a whole with respect to ground, also produce circulating currents in the transmission line. A transformer is then provided at the receiver end of the transmission line having a grounded midtap in a winding connected across the end of the line, so that substantially only the circulating currents produce an effect in the receiver, the currents such as noise currents, picked up by the two transmission line conductors in phase, producing no effect in the output of the latter transformer and therefore no efifect in the receiver.

In accordance with my present invention a simplified and efiicient system of the above character is provided wherein autotransformers are employed both to couple the antenna to the transmission line and to couple the transmission line 40 to the receiver, and capacitors heretofore employed in the coupling means between the antenna and the transmission line are eliminated.

It is a further feature of my invention that a circuit, anti-resonant at a predetermined frequency in the short wave range at which dipole operation is less efficient than T antenna operation, is provided whereby the midtap on the transformer connecting the transmission line to the receiver is not grounded, the antenna system then oscillating at this predetermined frequency, as a Whole. a

The novel features which are considered to be characteristic of my invention are set forth with particularity in the appended claims. My 5 invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing, which is a diagrammatic representation of an all-wave radio receiving system in which my invention has been embodied. In the drawing, the single figure represents a radio receiving system or like system including aload device such as a radio receiver l of the all-wave type having input terminals 2 and 3. The numeral 4 designates an antenna which may be, for example, a conventional doublet or dipole having oppositely extending tops 5 and 6. A transmission line or lead-in l is provided preferably of the type comprising a twisted pair of conductors 8 and 9, or two conductors closely adjacent to each other throughout their length. To couple the antenna 4 to the transmission line I, I provide a single winding or autotransformer l comprising a section II at one extremity thereof connected at taps I 2 and I 3 respectively to the inner ends of the antenna tops and 6, a section M at the opposite or outer extremity of the autotransformer connected at taps l5 and I6 respectively to the upper ends of the conductors 8 and 9 of transmission line 1, and an intermediate section ll between taps l3 and IS. The winding or autotransformer I0 is of the tight coupling type.

To couple the transmission line I to the receiver I, I provide a transformer I8 comprising a single winding or autotransformer IQ of the tight coupling type and a winding tightly coupled thereto. The primary 2| of autotransformer Winding i 9 is connected at its opposite extremities to the lower ends of the transmission line conductors 8 and 9 and is provided with a midtap 22. The secondary of autotransformer winding l9 includes that section 23 of primary 2| which extends between the midtap 22 and the connection point 24 of one of the line conductors, as 8, and a section 25 extending from connection point 24 to the upper extremity of the autotransfornier winding l9, which is connected to the antenna terminal 2 of the radio receiver l. One terminal of winding 2!] is connected to midtap 22, and connections including a condenser 26, having a high impedance for oscillations in the long wave bands and a low impedance for oscillation in the short wave bands, are provided between the other terminal of winding 20 and antenna terminal 2. The capacitor 26 can often be advantageously chosen to resonate with the secondary 20 in the high frequency band to improve reception. The other receiver terminal 3 is grounded, and connections including a circuit 21, constituted by a capacitance 28 and an inductance 29 and tuned to a predetermined relatively high frequency, are provided between the grounded terminal 3 and the midtap 22 of primary 2 In operation, when the all-wave receiver is adjusted for reception over a high frequency band other than that to which circuit 21 is tuned-as will be explained more fully hereinafter, the an tenna 4 operates. as a dipole, currents circulating therein, from one top portion to the other, through the autotransformer section H functioning as a primary to induce currents in section M which functions as a secondary. Currents from secondary section i4 circulate in the transmission line 1 and in the primary 2| of transformer |8 thereby inducing currentsin sec: ondary 20 from which the currents are supplied to receiver antenna terminal 2 and ground terminal 3 through condenser 26 which is of negligibly low impedance for the high frequency, and

, through circuit '21, which is of low impedance for all frequencies except its predetermined frequency. Secondary 20 and condenser 26, forming a series circuit across the receiver terminals, have, preferably, such characteristics that this series circuit resonates at about seven megacycles, which causesreception in'the six and thenine and five-tenths megacycle bands to be better than would be the case if the capacity of condenser 26 were chosen merely to provide high impedance in the low frequency bands and low impedance in'the high frequency bands. Any noise or other currents picked up by the conductors 8 and 9 of the transmission line 1 tend to flow in the same phase through the opposite halves of primary 2|, the midtap 22 of which is grounded through circuit 27, and are thus substantially canceled out. 7

When the receiver 1 is adjusted for reception over the broadcast or other low frequency bands, the impedance of the sections H, M and ll of antenna coupling coil or autotransformer Ill and the primary 2|of'autotransformer i9 being relatively low at these low frequencies, currents oscillate freely-in the circuit including the two antenna wires or tops 5 and is functioning as a single antenna, windings H, H and Id of transformer l0, transmission line conductors 8 and 9 operating inparallel, winding 2| of autotransformer l9, circuit 21, and ground. In autotransformer H! the oscillating currents in winding section |1 functioning as a primary induce currents in winding section l4 functioning as a secondary. The currents in section M then circulate in the opposite conductors 8 and 9 of transmission line I and in the primary 2| of autotransformer I9. Corresponding currents are then induced in sections 23 and 25 constituting the low frequency secondary which is connected across the receiver terminals through the circuit 21 in the connections between receiver grounded terminal 3 and the tap 2| of transformer I9, the latter circuit 21 being of negligibly low impedance for currents of the broadcast and other low frequency bands. As in'the case of operation on the high frequency band, noise or other currents picked up by the transmission line tend to flow in the same phase through the opposite halves of primary'zl having grounded midtap 22, and are canceled out as before.

It hasbeen found that while operation of the antenna as a dipole as hereinabove explained insures satisfactory reception over the greater part of the short wave bands, signal response at the receiver tends to fall off perceptibly at about four megacycles. I have found that the signal response may be brought up to satisfactory strength by the provision of the circuit 21 which is tuned to that high frequency, in the present case approximately four megacycles, at which the lessened signal response is otherwise obtained. In operation of the system at this latter frequency, the transformer I8 is virtually disconnected from ground by the high impedance of tuned circuit 21 in the connections between midtap 22 and the grounded terminal 3 of receiver The antenna system as a whole, constituted by the antenna proper or horizontal wires 4 and the down-lead I, then operates as a usual T antenna to supply currentsat the predetermined frequency through the antenna terminal 2 to the receiver Thus, while the resulting T antenna operation at four megacycles due to the action of the tuned circuit 21 does not provide for noise reductionat the frequency of four megacycles, the desirable result is obtained that the signal response throughout the short wave bands is caused to be maintained substantially uniform at a satisfactorily high level.

The radio receiver system in accordance with my invention has been described hereinabove in connection with a single radio receiver of the all-wave type. It will be readily understood, however, that the system is easily adaptable to reception of the short wave and long wave signals respectively bydifferent receivers supplied from the same antenna 4 and transmission line 1.-

My invention has been described herein in a particular-embodiment for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a dipole antenna, radio apparatus adapted to receive long and short waves, a transmission line adapted to have long and short wave currents circulating therein, means ,to couple said antenna to said transmission line 'a transmission line arranged to have long and short wave currents circulating therein, means constituted by an autotransformer to couple said antenna to said transmission line, and means to couple said transmission line to said radio'receiver comprising an autotransformer having a primary connected at its midtap to the grounded terminal of said receiver and a secondary connected across the antenna terminal of said receiver and said grounded terminal, said secondnamed coupling means further comprising a secondary in inductive relation with said primary and connected across said terminals through a condenser having a high impedance for long waves and a low impedance for short waves.

3. In combination, a dipole antenna, a radio receiver adapted to receive long and short waves, a transmission line adapted to have long and short wave currents circulating therein, means to couple said antenna to said transmission line for lon and short waves, means to couple said transmission line to said receiver for long and short waves comprising a transformer having a primary connected at its midtap to the grounded terminal of said receiver and a secondary connected across the antenna terminal of said receiver and said grounded terminal through a condenser having a high impedance for long waves and a low impedance for short waves, and a circuit tuned to a predetermined high frequency in the connections between said midtap and said grounded terminal, whereby said antenna and said transmission line operate together as a T antenna at said predetermined frequency.

4. In combination, a dipole antenna, an allwave radio receiver, a transmission line adapted to have long and short wave currents circulating therein, means constituted by an autotransformer to couple said antenna to said line, said autotransformer having two sections connected respectively across the inner extremities of said antenna and the upper extremities of said line and a section between said two sections, and means to couple said receiver to said line comprising an autotransformer having a primary connected at its midtap to the grounded terminal of said receiver, a secondary connected across the antenna terminal and the grounded terminal of said receiver, and another secondary in inductive relation with said primary and connected across said terminals through a condenser, whereby long and short wave currents circulating in said line are supplied respectively to said receiver through said firstnamed and said second-named secondaries.

5. In combination, a dipole antenna, a radio receiver adapted to receive long and short waves,

a transmission line arranged to have long and short wave currents circulating therein, means to couple said antenna to said line, and means to couple said line to said receiver comprising an autotransformer having a primary connected at its midtap to the grounded terminal of said receiver and a secondary connected across the antenna terminal of said receiver and said grounded terminal, said second-named means further com prising a series circuit connected across said terminal including a secondary in inductive relation with said primary and a condenser, said condenser having such capacity that said series circuit resonates at a predetermined frequency in the short wave range.

7 ROBERT B. DOME. 

